check derivation of mod_leading_zeros

Signed-off-by: Andrew Whitehead <[email protected]>

src/modular/boxed_monty_form.rs

@@ -327,12 +327,14 @@ fn convert_to_montgomery(integer: &mut BoxedUint, params: &BoxedMontyParams) {
 
 #[cfg(test)]
 mod tests {
-    use super::{BoxedMontyForm, BoxedMontyParams, BoxedUint, Odd};
+    use super::{BoxedMontyForm, BoxedMontyParams, BoxedUint, Limb, Odd};
 
     #[test]
     fn new_params_with_valid_modulus() {
         let modulus = Odd::new(BoxedUint::from(3u8)).unwrap();
-        BoxedMontyParams::new(modulus);
+        let params = BoxedMontyParams::new(modulus);
+
+        assert_eq!(params.mod_leading_zeros, Limb::BITS - 2);
     }
 
     #[test]

src/modular/const_monty_form/macros.rs

@@ -84,3 +84,16 @@ macro_rules! const_monty_form {
         $crate::modular::ConstMontyForm::<$modulus, { $modulus::LIMBS }>::new(&$variable)
     };
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::modular::ConstMontyParams;
+    use crate::{Limb, U64};
+
+    #[test]
+    fn new_params_with_valid_modulus() {
+        impl_modulus!(Mod, U64, "0000000000000003");
+
+        assert_eq!(Mod::MOD_LEADING_ZEROS, core::cmp::min(Limb::BITS - 1, 62));
+    }
+}

src/modular/monty_form.rs

@@ -337,3 +337,16 @@ impl<const LIMBS: usize> zeroize::Zeroize for MontyForm<LIMBS> {
         self.params.zeroize();
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{Limb, MontyParams, Odd, Uint};
+
+    #[test]
+    fn new_params_with_valid_modulus() {
+        let modulus = Odd::new(Uint::from(3u8)).unwrap();
+        let params = MontyParams::<1>::new(modulus);
+
+        assert_eq!(params.mod_leading_zeros, Limb::BITS - 2);
+    }
+}